Machines using a coiled spring "snake" to clean drains have long been known. Most machines in use today utilize a power source to rotate the coil,making the action of the snake inserted into the drain more effective. The best known of such machines, and the device upon which the preferred embodiment of the present invention is based, is the familiar Roto-Rooter.TM. machine.
In certain conditions of sludge or ice blockage, however, the snake used alone may be of limited effectiveness. The snake may penetrate the soft sludge easily, but the blockage re-forms behind the snake as it is withdrawn. What is needed under such conditions is a sufficient flow of water at the head, or free, end of the snake to wash the sludge down the sewer as the snake is pulled back toward the operator.
Several prior inventions have attempted to combine a snake with a water injection system (see Sato, U.S. Pat. No. 3,959,840; or Ciaccio, U.S. Pat. No. 3,370,599) through insertion of a tube into the inside of the coiled spring snake. These inventions represented the use of a blast of high-pressure water (as much as 10,000 p.s.i. in the Ciaccio machine) to punch through blockages.
These very high pressures require extremely heavy and rugged (hence expensive) components. The tubes must have thick walls to withstand the pressure used. On the other hand, "head" losses caused by friction between the water and the walls of the tube are aggravated under high pressure conditions, so large inside diameters are needed to achieve sufficient pressure at the working end of the snake. Thus the tubing needed becomes large and of limited flexibility. The Ciaccio machine uses tubing so large in outside diameter that a snake of over an inch in diameter is required to contain it. This is far too large for home drains, and its limited flexibility would make it difficult or impossible for the snake to traverse the bends commonly found in house plumbing. Were the tubing made much thinner, it would not be able to hold up under the tremendous pressures used.
Any machine which needs such high pressure also requires some additional machinery to generate the pressures, limiting the portability of the device. This is a major factor in home work, where the sewer drain is usually located in a cellar or other cramped quarters. The extra machinery adds both weight and bulk. Ciaccio is mounted on a vehicular trailer, and Sato has an external pump and reservoir set-up.
The machines noted are built with fixed drums, at least in part because of the difficulty of preventing leakage at the pressures used. Thus, the user must transport the heavier and thicker spring and tube combination, even when the water is not needed. If an especially thin coil is needed, another machine will have to be brought in.